Mean Arterial Pressure (MAP) Calculator
Compute mean arterial pressure from a blood-pressure reading — the perfusion pressure that matters at the bedside and in the cath lab.
What is mean arterial pressure?
Mean arterial pressure (MAP) is the average pressure in your arteries over one cardiac cycle. It matters more than the systolic number alone because it is the pressure actually driving blood into your organs. When clinicians talk about keeping the kidneys, brain, and gut perfused, MAP is the number they watch.
The MAP formula
The standard estimate is:
MAP = DBP + ⅓ × (SBP − DBP)
An equivalent way to write it is MAP = (SBP + 2 × DBP) ÷ 3. Both weight the diastolic pressure twice as heavily as the systolic, because at normal heart rates the heart spends roughly two-thirds of each cycle in diastole. (At fast heart rates diastole shortens, so the estimate drifts; an arterial line measures the true MAP directly by integrating the pressure waveform.)
Normal values and targets
| MAP | Interpretation |
|---|---|
| 70–100 mmHg | Normal |
| ≥ 65 mmHg | Usual minimum target to perfuse vital organs |
| < 60 mmHg | Organ perfusion at risk (e.g., kidneys, brain) |
A MAP of at least 65 mmHg is the widely used floor for adequate organ perfusion, and it is the default resuscitation target in sepsis and many shock states. Patients with chronic hypertension or raised intracranial pressure may need a higher MAP to perfuse organs that have re-set their autoregulation.
What determines MAP
Physiologically, MAP ≈ cardiac output × systemic vascular resistance (plus the central venous pressure). That relationship explains the two ways to raise a low MAP: increase the flow (fluids, inotropes) or increase the resistance (vasopressors). It also explains the shock profiles — a low MAP with a low resistance points to distributive (septic) shock, while a low MAP with a high resistance fits cardiogenic or hypovolaemic shock. Explore this in the shock hemodynamics guide and the SVR/PVR calculator.
References
- Surviving Sepsis Campaign and standard critical-care references on MAP targets. AHA.
Educational reference only — not a substitute for clinical judgement.
Frequently asked questions
How do you calculate mean arterial pressure?
MAP = diastolic BP + ⅓ × (systolic BP − diastolic BP), which is the same as (systolic + 2 × diastolic) ÷ 3. Diastole is weighted twice because the heart spends about two-thirds of each cycle in diastole.
What is a normal mean arterial pressure?
About 70–100 mmHg. A MAP of at least 65 mmHg is generally needed to perfuse the vital organs, and below 60 mmHg organ perfusion is at risk.
Why is MAP more useful than systolic pressure?
It reflects the average pressure driving blood to the organs across the whole cardiac cycle, not just the peak, so it better predicts organ perfusion.
What is a dangerously low MAP?
A MAP under about 60 mmHg risks under-perfusing the kidneys and brain. Most shock protocols aim to keep the MAP at 65 mmHg or above.
Why is the diastolic pressure weighted more in the MAP formula?
Because at normal heart rates roughly two-thirds of each cardiac cycle is spent in diastole, so diastolic pressure contributes more to the average.
What determines mean arterial pressure?
MAP is approximately cardiac output multiplied by systemic vascular resistance (plus central venous pressure). Raising a low MAP means increasing flow, resistance, or both.
What MAP target is used in sepsis?
A MAP of at least 65 mmHg is the standard initial resuscitation target in septic shock, individualised to the patient.